debian/patches/extra/0002-memory-prevent-dma-reentracy-issues.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Alexander Bulekov <alxndr@bu.edu>
   3 Date: Sat, 4 Feb 2023 23:07:34 -0500
   4 Subject: [PATCH] memory: prevent dma-reentracy issues
   5
   6 Add a flag to the DeviceState, when a device is engaged in PIO/MMIO/DMA.
   7 This flag is set/checked prior to calling a device's MemoryRegion
   8 handlers, and set when device code initiates DMA.  The purpose of this
   9 flag is to prevent two types of DMA-based reentrancy issues:
  10
  11 1.) mmio -> dma -> mmio case
  12 2.) bh -> dma write -> mmio case
  13
  14 These issues have led to problems such as stack-exhaustion and
  15 use-after-frees.
  16
  17 Summary of the problem from Peter Maydell:
  18 https://lore.kernel.org/qemu-devel/CAFEAcA_23vc7hE3iaM-JVA6W38LK4hJoWae5KcknhPRD5fPBZA@mail.gmail.com
  19
  20 Resolves: https://gitlab.com/qemu-project/qemu/-/issues/62
  21 Resolves: https://gitlab.com/qemu-project/qemu/-/issues/540
  22 Resolves: https://gitlab.com/qemu-project/qemu/-/issues/541
  23 Resolves: https://gitlab.com/qemu-project/qemu/-/issues/556
  24 Resolves: https://gitlab.com/qemu-project/qemu/-/issues/557
  25 Resolves: https://gitlab.com/qemu-project/qemu/-/issues/827
  26 Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1282
  27
  28 Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
  29 Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
  30 Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
  31 Acked-by: Peter Xu <peterx@redhat.com>
  32 (picked-up from https://lists.nongnu.org/archive/html/qemu-devel/2023-02/msg01142.html)
  33 Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
  34 ---
  35  include/hw/qdev-core.h |  7 +++++++
  36  softmmu/memory.c       | 17 +++++++++++++++++
  37  softmmu/trace-events   |  1 +
  38  3 files changed, 25 insertions(+)
  39
  40 diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
  41 index bd50ad5ee1..7623703943 100644
  42 --- a/include/hw/qdev-core.h
  43 +++ b/include/hw/qdev-core.h
  44 @@ -162,6 +162,10 @@ struct NamedClockList {
  45      QLIST_ENTRY(NamedClockList) node;
  46  };
  47
  48 +typedef struct {
  49 +    bool engaged_in_io;
  50 +} MemReentrancyGuard;
  51 +
  52  /**
  53   * DeviceState:
  54   * @realized: Indicates whether the device has been fully constructed.
  55 @@ -194,6 +198,9 @@ struct DeviceState {
  56      int alias_required_for_version;
  57      ResettableState reset;
  58      GSList *unplug_blockers;
  59 +
  60 +    /* Is the device currently in mmio/pio/dma? Used to prevent re-entrancy */
  61 +    MemReentrancyGuard mem_reentrancy_guard;
  62  };
  63
  64  struct DeviceListener {
  65 diff --git a/softmmu/memory.c b/softmmu/memory.c
  66 index b1a6cae6f5..e4d2268d32 100644
  67 --- a/softmmu/memory.c
  68 +++ b/softmmu/memory.c
  69 @@ -533,6 +533,7 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
  70      uint64_t access_mask;
  71      unsigned access_size;
  72      unsigned i;
  73 +    DeviceState *dev = NULL;
  74      MemTxResult r = MEMTX_OK;
  75
  76      if (!access_size_min) {
  77 @@ -542,6 +543,19 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
  78          access_size_max = 4;
  79      }
  80
  81 +    /* Do not allow more than one simultanous access to a device's IO Regions */
  82 +    if (mr->owner &&
  83 +        !mr->ram_device && !mr->ram && !mr->rom_device && !mr->readonly) {
  84 +        dev = (DeviceState *) object_dynamic_cast(mr->owner, TYPE_DEVICE);
  85 +        if (dev) {
  86 +            if (dev->mem_reentrancy_guard.engaged_in_io) {
  87 +                trace_memory_region_reentrant_io(get_cpu_index(), mr, addr, size);
  88 +                return MEMTX_ERROR;
  89 +            }
  90 +            dev->mem_reentrancy_guard.engaged_in_io = true;
  91 +        }
  92 +    }
  93 +
  94      /* FIXME: support unaligned access? */
  95      access_size = MAX(MIN(size, access_size_max), access_size_min);
  96      access_mask = MAKE_64BIT_MASK(0, access_size * 8);
  97 @@ -556,6 +570,9 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
  98                          access_mask, attrs);
  99          }
 100      }
 101 +    if (dev) {
 102 +        dev->mem_reentrancy_guard.engaged_in_io = false;
 103 +    }
 104      return r;
 105  }
 106
 107 diff --git a/softmmu/trace-events b/softmmu/trace-events
 108 index 22606dc27b..62d04ea9a7 100644
 109 --- a/softmmu/trace-events
 110 +++ b/softmmu/trace-events
 111 @@ -13,6 +13,7 @@ memory_region_ops_read(int cpu_index, void *mr, uint64_t addr, uint64_t value, u
 112  memory_region_ops_write(int cpu_index, void *mr, uint64_t addr, uint64_t value, unsigned size, const char *name) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" size %u name '%s'"
 113  memory_region_subpage_read(int cpu_index, void *mr, uint64_t offset, uint64_t value, unsigned size) "cpu %d mr %p offset 0x%"PRIx64" value 0x%"PRIx64" size %u"
 114  memory_region_subpage_write(int cpu_index, void *mr, uint64_t offset, uint64_t value, unsigned size) "cpu %d mr %p offset 0x%"PRIx64" value 0x%"PRIx64" size %u"
 115 +memory_region_reentrant_io(int cpu_index, void *mr, uint64_t offset, unsigned size) "cpu %d mr %p offset 0x%"PRIx64" size %u"
 116  memory_region_ram_device_read(int cpu_index, void *mr, uint64_t addr, uint64_t value, unsigned size) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" size %u"
 117  memory_region_ram_device_write(int cpu_index, void *mr, uint64_t addr, uint64_t value, unsigned size) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" size %u"
 118  memory_region_sync_dirty(const char *mr, const char *listener, int global) "mr '%s' listener '%s' synced (global=%d)"